U.S. patent application number 15/263943 was filed with the patent office on 2017-03-23 for hard disk drive and pivot assembly bearing device.
This patent application is currently assigned to MINEBEA CO., LTD.. The applicant listed for this patent is MINEBEA CO., LTD.. Invention is credited to Daiki KOBAYASHI, Weihong YANG.
Application Number | 20170084297 15/263943 |
Document ID | / |
Family ID | 58282978 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170084297 |
Kind Code |
A1 |
YANG; Weihong ; et
al. |
March 23, 2017 |
HARD DISK DRIVE AND PIVOT ASSEMBLY BEARING DEVICE
Abstract
A hard disk drive according to an embodiment of the present
invention includes a pivot assembly bearing device with a shaft,
rolling bearings and a sleeve, a cylindrical convex portion formed
in a cover member at the upper side, protruding inward, and fixed
to an upper end surface of the shaft, a convex portion formed on a
base member at the lower side, protruding inward, and fixed to a
lower end surface of the shaft, and a labyrinth gap formed by
opposing an outer peripheral surface of the convex portion to an
inner peripheral surface of a sleeve in a radial direction and/or
by opposing an outer peripheral surface of the convex portion to
the inner peripheral surface of the sleeve in a radial
direction.
Inventors: |
YANG; Weihong; (Yokohama,
JP) ; KOBAYASHI; Daiki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MINEBEA CO., LTD. |
Nagano |
|
JP |
|
|
Assignee: |
MINEBEA CO., LTD.
Nagano
JP
|
Family ID: |
58282978 |
Appl. No.: |
15/263943 |
Filed: |
September 13, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16C 33/80 20130101;
G11B 19/2036 20130101; F16C 19/06 20130101; G11B 5/4813 20130101;
F16C 35/07 20130101; F16C 19/54 20130101 |
International
Class: |
G11B 5/48 20060101
G11B005/48 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2015 |
JP |
2015-184133 |
Claims
1. A hard disk drive including a pivot assembly bearing device
supporting a swing arm, the pivot assembly bearing device having a
rolling bearing, a shaft and a sleeve, the rolling bearing having
an outer race and an inner race, the shaft having an outer
peripheral surface on which the inner race is fixed, the sleeve
having an inner peripheral surface on which the outer race is
fixed, the hard disk drive comprising: a first convex portion that
is cylindrical and/or a second convex portion that is cylindrical,
the first convex portion being formed in a cover member positioned
on an upper side of the hard disk drive, protruding toward an
inside of the hard disk drive, and being fixed to an upper end
surface of the shaft, the second convex portion being formed on a
base member being positioned on a lower side of the hard disk
drive, protruding toward an inside of the hard disk drive, and
being fixed to a lower end surface of the shaft, an outer
peripheral surface of the first convex portion and/or an outer
peripheral surface of the second convex portion being opposed to an
inner peripheral surface of the sleeve in a radial direction to
form a labyrinth gap.
2. The hard disk drive according to claim 1, further comprising an
annular sealing member having an upper surface disposed opposite to
the first convex portion, having a lower surface disposed opposite
to the inner race of the rolling bearing, having an inner
peripheral surface disposed opposite to an outer peripheral surface
of the shaft, and having an outer peripheral surface fixed to at
inner peripheral surface of the sleeve.
3. The hard disk drive according to claim 2, further comprising a
cut-out portion between the upper surface and the outer peripheral
surface of the sealing member.
4. The hard disk drive according to claims 1, wherein the labyrinth
gap includes a gap formed by opposing an upper end surface of the
sleeve and the cover member and/or a lower end surface of the
sleeve and an inner surface of the base member.
5. The hard disk drive according to claim 1, wherein the labyrinth
gap has a gap width of less than 0.37 mm in the proximity of an
outlet of the labyrinth gap.
6. A hard disk drive including a pivot assembly bearing device to
support a swing arm, the pivot assembly bearing device having a
rolling bearing and a shaft and being fitted into a mounting hole
formed in the swing arm, the rolling bearing having an outer race
and an inner race, the shaft having an outer peripheral surface on
which the inner race is fixed, the hard disk drive comprising: a
first convex portion that is cylindrical and/or a second convex
portion that is cylindrical, the first convex portion being formed
in a cover member positioned on an upper side of the hard disk
drive, protruding toward an inside of the hard disk drive, and
being fixed to an upper end surface of the shaft, the second convex
portion being formed on a base member positioned on a lower side of
the hard disk drive, protruding toward an inside of the hard disk
drive, and being fixed to a lower end surface of the shaft, an
outer peripheral surface of the first convex portion and/or an
outer peripheral surface of the second convex portion being opposed
to an inner peripheral surface of the mounting hole of the swing
arm in a radial direction to form a labyrinth gap.
7. The hard disk drive according to claim 6, further comprising an
annular sealing member having an upper surface disposed opposite to
the first convex portion, having a lower surface disposed opposite
to the rolling bearing, having an inner peripheral surface disposed
opposite to an outer peripheral surface of the shaft, and having an
outer peripheral surface fixed.
8. The hard disk drive according to claim 7, further comprising a
cylindrical sleeve having an inner peripheral surface fixed to the
outer race, having an outer peripheral surface fitted into the
mounting hole of the swing arm, an upper end surface disposed
opposite to the first convex portion through a gap, having a lower
end surface disposed opposite to the second convex portion through
a gap, and having the cuter peripheral surface of the sealing
member fixed to an inner peripheral surface of the sleeve.
9. The bard disk drive according to claim 7, further comprising a
cut-out portion between the upper surface and the outer peripheral
surface of the sealing member.
10. The hard disk drive according to claim 6, wherein the labyrinth
gap includes a gap formed by opposing an upper end surface of the
mounting hole of the swing arm to an inside surface of the cover
member and/or opposing a lower end surface of the mounting hole of
the swing arm to an inner surface of the base member.
11. The hard disk drive according to claim 6, wherein the labyrinth
gap has a gap width of less than 0.37 mm in the proximity of an
outlet of the labyrinth gap.
12. A pivot assembly bearing device swingably supporting a swing
arm of a hard disk drive, the pivot assembly comprising: a shaft
having a flange portion on a lower side; a cylindrical sleeve
disposed coaxially with the shaft; and a pair of rolling bearings
axially spaced between the shaft and the sleeve, the sleeve being
longer than the shaft, the sleeve having an upper end surface
positioned above an upper end surface of the shaft, and a lower end
surface being positioned below a lower surface of the flange
portion.
13. The pivot assembly bearing device according to claim 12, having
an annular sealing member fixed to the sleeve at a position above a
rolling bearing of the pair of rolling bearings that is disposed on
an upper side of the shaft, the sealing member having an upper
surface positioned below the upper end surface of the shaft.
14. The pivot assembly bearing device according to claim 13, having
a cut-out portion between an upper surface of the sealing member
and an outer peripheral surface or an inner peripheral surface of
the sealing member.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] The present application claims priority to and incorporates
by reference the entire contents of Japanese Patent Application No.
2015-184133 filed in Japan on Sep. 17, 2015.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a hard disk drive including
a pivot assembly bearing device, and a pivot assembly bearing
device.
[0004] 2. Description of the Related Art
[0005] Hard disk drives are conventionally known, which have a
pivot assembly bearing device configured to support a swing arm
having a magnetic head for recording and reproducing signals. FIG.
12 is a cross-sectional view of a configuration of a conventional
pivot assembly bearing device. As illustrated in FIG. 12, the
conventional pivot assembly bearing device 100 has a configuration
in which a cylindrical sleeve 101 relatively rotatably supports a
cylindrical shaft 103 through a pair of axially-spaced rolling
bearings 102 each including an inner race 102a, an outer race 102b,
and rolling bodies 102c. The pivot assembly bearing device 100
having such a configuration fixes the shaft 103 to a base member of
a hard disk drive, fits the sleeve 101 into a mounting hole 104
formed in a swing arm and swingably supports the swing arm.
[0006] With recent increase in processing speed, and capacity and
density of information recorded in hard disk drives, the distance
between a magnetic head and a magnetic disk has been reduced, and
even fine foreign matter which has not been so significant causes
failure of the hard disk drives. Thus, it is increasingly important
to maintain cleanliness in the hard disk drives. The rolling
bearing uses lubricant, but out-particles are generated by
gasification or microparticulation of the lubricant, and a
technique for keeping the out-particles from reducing cleanliness
in a hard disk drive is demanded. In consideration of such a
background, a pivot assembly bearing device is proposed, which
keeps out-particles from reducing cleanliness in a hard disk drive
(e.g., see Japanese Patent Application Laid-open No. 2013-48005).
In particular, a technique is proposed in which sealing plates 105
and 106 are disposed at an upper end portion of the sleeve 101 to
form a labyrinth gap, and the out-particles are kept from
scattering outside the pivot assembly bearing device 100, as
illustrated in FIG. 12.
[0007] However, as a result of an extensive study, the inventors of
the present invention have found that even if sealing performance
of a single pivot assembly bearing device is improved, scattering
of the out-particles outside the pivot assembly bearing device
cannot be effectively suppressed. FIG. 13 is a schematic diagram
illustrating airflow around the conventional pivot assembly bearing
device. In the hard disk drives, airflow is generally generated
around the magnetic disk with the rotation of the magnetic disk. As
indicated by an arrow A1 in FIG. 13, airflow passing through the
pivot assembly bearing device partially flows into the pivot
assembly bearing device 100, from a gap between a cover member 107
of the hard disk drive and an axial end surface of the sleeve 101.
Airflow flowing into the pivot assembly bearing device 100 is
discharged from the pivot assembly bearing device 100 to the
outside, as indicated by an arrow A2 in FIG. 13. Therefore, the
out-particles retained in the pivot assembly bearing device 100 are
scattered outside the pivot assembly bearing device 100 by this
airflow, and the scattered particles reduce the cleanliness in the
hard disk drive.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to at least
partially solve the problems in the conventional technology.
[0009] A hard disk drive according to one aspect of the present
invention may include a pivot assembly bearing device, the pivot
assembly bearing device having a rolling bearing, a shaft and a
sleeve and supporting a swing arm, the rolling bearing having an
outer race and an inner race, the shaft having an outer peripheral
surface on which the inner race is fixed, the sleeve having an
inner peripheral surface on which the outer race is fixed. The hard
disk drive comprises: a first convex portion that is cylindrical
and/or a second convex portion that is cylindrical, the first
convex portion being formed on a cover member positioned on an
upper side of the hard disk drive, protruding toward an inside of
the hard disk drive, and being fixed to an upper end surface of the
shaft, the second convex portion being formed on a base member
being positioned on a lower side of the hard disk drive, protruding
toward an inside of the hard disk drive, and being fixed to a lower
end surface of the shaft, an outer peripheral surface of the first
convex portion and/or an outer peripheral surface of the second
convex portion being opposed to an inner peripheral surface of the
sleeve in a radial direction to form a labyrinth gap.
[0010] The above and other objects, features, advantages and
technical and industrial significance of this invention will be
better understood by reading the following detailed description of
presently preferred embodiments of the invention, when considered
in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective view of an overall configuration of
a hard disk drive according to an embodiment of the present
invention;
[0012] FIG. 2 is a cross-sectional view of a configuration of a
pivot assembly bearing device according to a first embodiment of
the present invention;
[0013] FIG. 3 is a partially enlarged cross-sectional view of a
configuration around a rolling bearing in the pivot assembly
bearing device illustrated in FIG. 2;
[0014] FIG. 4 is a schematic diagram illustrating airflow around
the pivot assembly bearing device according to the first embodiment
of the present invention;
[0015] FIG. 5 is a cross-sectional view of a configuration of a
modification of the pivot assembly bearing device illustrated in
FIG. 2;
[0016] FIG. 6 is a cross-sectional view of a configuration of a
modification of a cut-out portion illustrated in FIG. 3;
[0017] FIG. 7 is a cross-sectional view of a configuration of a
modification of the cut-out portion illustrated in FIG. 3;
[0018] FIG. 8 is a cross-sectional view of a configuration of a
modification of the cut-out portion illustrated in FIG. 3;
[0019] FIG. 9 is a cross-sectional view of a configuration of a
pivot assembly bearing device according to a second embodiment of
the present invention;
[0020] FIG. 10 is a cross-sectional view of a configuration of a
modification of the pivot assembly bearing device illustrated in
FIG. 9;
[0021] FIG. 11 is a graph illustrating examples of maximum flow
rates of airflow on the respective outlet sides of a pivot assembly
bearing device according to the present invention and a
conventional pivot assembly bearing device;
[0022] FIG. 12 is a cross-sectional view of a configuration of a
conventional pivot assembly bearing device; and
[0023] FIG. 13 is a schematic diagram illustrating airflow around
the conventional pivot assembly bearing device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] A configuration and operation of a hard disk drive according
to an embodiment of the present invention is described below with
reference to the drawings. In the following description, the terms
such as "upper" and "lower" are only used to indicate directions in
the drawings, and the terms are not intended to limit the position
of the hard disk drive in the present invention.
Overall Configuration of Hard Disk Drive
[0025] First, an overall configuration of the hard disk drive
according to an embodiment of the present invention is described
with reference to FIG. 1.
[0026] FIG. 1 is a perspective view of the overall configuration of
the bard disk drive according to an embodiment of the present
invention. As illustrated in FIG. 1, a hard disk drive 1 according
to an embodiment of the present invention includes a swing arm 3
swingably supported by a pivot assembly bearing device 2 fitted
into a mounting hole. The pivot assembly bearing device 2 is
described later. In this hard disk drive 1, a magnetic head 4
disposed at an end of the swing arm 3 moves on a magnetic disk 5
being rotated, records information on the magnetic disk 5, and
reads the information recorded in the magnetic disk 5.
Configuration of Pivot Assembly Bearing Device
First Embodiment
[0027] Next, a configuration of the pivot assembly bearing device
according to a first embodiment of the present invention is
described with reference to FIGS. 2 to 4. FIG. 2 is a
cross-sectional view of the configuration of the pivot assembly
bearing device according to the first embodiment of the present
invention. FIG. 3 is a partially enlarged cross-sectional view of a
configuration around a rolling bearing in the pivot assembly
bearing device illustrated in FIG. 2. FIG. 4 is a schematic diagram
illustrating airflow around the pivot assembly bearing device
according to the first embodiment of the present invention.
[0028] As illustrated in FIG. 2, the pivot assembly bearing device
2 according to the first embodiment of the present invention
includes a pair of upper and lower rolling bearings 23 disposed
between a cylindrical shaft 21 and a cylindrical sleeve 22. Each of
the rolling bearings 23 includes an inner race 23a fixedly bonded
on en outer peripheral surface 21a of the shaft 21, an outer race
23b fixedly bonded on an inner peripheral surface 22b of the sleeve
22, a plurality of rolling bodies 23c provided between the inner
race 23a and the outer race 23b, and an annular holder 23d
configured to hold the rolling bodies 23c. The sleeve 22 is longer
than the shaft 21, and has an upper end surface 22f disposed to be
positioned above an upper end surface 21f of the shaft 21, and a
lower and surface 22d disposed to be positioned below a lower
surface of an outer flange 21b of the shaft 21 which is described
later. Such a configuration allows the pivot assembly bearing
device 2 incorporated into the hard disk drive to form a labyrinth
gap as described later.
[0029] The shaft 21 is a cylindrical member having an outer flange
21b radially protruding, at a lower end portion. The outer flange
21b has an upper surface 21b1 on the inner peripheral side, and a
lower end surface 23a1 of the inner race 23a of the upper rolling
bearing 23 disposed on the axially lower side abuts on the upper
surface 21b1. By this way, the inner race 23a of the rolling
bearing 23 at the axially lower side is positioned with respect to
the shaft 21 in the vertical direction (axial direction). The outer
flange 21b has an outer peripheral surface 21b2 disposed opposite
to the inner peripheral surface 22b of the sleeve 22 through a gap.
The outer flange 21b has an upper surface on the outer peripheral
side, and an annular stepped portion 21c is formed on the upper
surface to avoid making contact with the outer race 23b of the
rolling bearing 23 disposed on the axially lower side.
[0030] The outer flange 21b has a lower surface 21b3 fixed on an
upper surface (protruding surface) of a cylindrical convex portion
11a (second convex portion). The cylindrical convex portion 11a is
formed on a base member 11 positioned on the lower side of the hard
disk drive 1, and protruding toward the inside of a casing of the
hard disk drive 1. An annular bonding area 21d extending in a
circumferential direction is formed at a position on the outer
peripheral surface 21a of the shaft 21, corresponding to each of
the rolling bearings 23 disposed vertically. A boss 21e and a
through-hole disposed coaxially with the shaft 21 are provided in a
lower end surface of the shaft 21. The boss 21e is fitted to an
inner peripheral surface of the convex portion 11a. Screw threads
are formed in an upper end portion and a lower end portion of the
through-hole, and screws not illustrated are tightened into the
screw threads. Therefore, the pivot assembly bearing device 2 is
fixed to the base member 11 on the lower side of the hard disk
drive 1 through the convex portion 11a, and is fixed to a cover
member 12 on the upper side of the hard disk drive device through a
convex portion 12a.
[0031] The sleeve 22 has an outer peripheral surface 22a fixedly
fitted into an inner peripheral surface 31a of a mounting hole 31
formed in the swing arm 3 (see FIG. 1). A fixing method includes
bonding, press-fitting, or a tolerance ring, but any of them may be
used. A pair of upper and lower outer race fitting portions 22c to
which the outer races 23b of the rolling bearings 23 are fitted is
formed in the inner peripheral surface 22b of the sleeve 22, and
the outer races 23b of the pair of upper and lower rolling bearings
23 are correspondingly fitted to outer race fitting portions 22c.
Therefore, the pair of the rolling bearings 23 is positioned with
respect to the sleeve 22 in the axial direction (vertical
direction), and an axial distance (vertical interval) between the
upper and lower rolling bearings 23 is held at a predetermined
distance. Note that the outer flange 21b of the shaft 21 has an
outer diameter set smaller than a diameter of the outer race
fitting portion 22c of the sleeve 22, and larger than an inner
diameter of the outer race 23b of the rolling bearing 23.
[0032] The lower end surface 22d of the sleeve 22 is opposed to an
inner surface 11b of the base member 11 through a gap. Furthermore,
the sleeve 22 has a lower inner peripheral surface 22e opposed to
an outer peripheral surface 11a1 of the convex portion 11a through
a gap. Thus, the labyrinth gap having a plurality of bent portions
is formed between the outer peripheral surface 21b2 of the outer
flange 21b and the outer peripheral surface 11a1 of the convex
portion 11a, and the lower inner peripheral surface 22e of the
sleeve 22, and between the lower end surface 22d of the sleeve 22
and the inner surface 11b of the base member 11.
[0033] As illustrated in FIG. 3, in a space between the outer
peripheral surface 21a of the shaft 21 and the inner peripheral
surface 22b of the sleeve 22, an annular sealing member 24 is
disposed at an upper portion of the upper rolling bearing 23. An
inclined surface is formed at a corner between an upper surface 24a
and an outer peripheral surface of the sealing member 24 to provide
a cut-out portion 24a1. The sealing member 24 has an upper surface
24a which is disposed opposite to a lower surface 12a2 (protruding
surface) of the convex portion 12a (example of first convex
portion), through a gap. The convex portion 12a (example of first
convex portion) is formed on the cover member 12 positioned on the
upper side of the hard disk drive 1, and protrudes toward the
inside of the hard disk drive 1. Furthermore, the outer peripheral
surface of the sealing member 24 is fixedly bonded to the inner
peripheral surface 22b of the sleeve 22, and further an inner
peripheral surface 24b of the sealing member 24 is disposed
opposite to the outer peripheral surface 21a of the shaft 21,
through a gap. The sealing member 24 has a lower surface abutting
on the outer race 23b of the rolling bearing 23. Since a preload is
applied to the rolling bearing 23, an end surface of the inner race
23a is positioned slightly lower than an end surface of the outer
race 23b. Therefore, a minute gap communicating with the labyrinth
gap is formed between the lower surface of the sealing member 24
and the end surface of the inner race.
[0034] The inner peripheral surface 22b of the sleeve 22 is opposed
to an outer peripheral surface 12a1 of the convex portion 12a of
the cover member 12 through a gap. The upper end surface 22f of the
sleeve 22 is opposed to an inner surface 12b of the cover member 12
through a gap. Thus, the labyrinth gap having a plurality of bent
portions is formed between the outer peripheral surface 21a of the
shaft 21 and the inner peripheral surface 24b of the sealing member
24, between the lower surface 12a2 of the convex portion 12a and
the upper surface 24a of the sealing member 24, between the inner
peripheral surface 22b of the sleeve 22 and the outer peripheral
surface 12a1 of the convex portion 12a, and between the upper end
surface 22f of the sleeve 22 and the inner surface 12b of the cover
member 12.
[0035] As indicated by the arrow A3 in FIG. 4, according to the
hard disk drive 1 having such a configuration, the labyrinth gap
having the plurality of bent portions formed by opposing the inner
peripheral surface 22b of the sleeve 22 to the convex portion 12a
of the cover member 12 avoids airflow generated around the magnetic
disk 5 due to the rotation of the magnetic disk 5 entering the
pivot assembly bearing device 2. Further, even if the airflow
enters the pivot assembly bearing device 2, as the labyrinth gap
has the plurality of bent portions with a narrow gap width, the
flow rate of the airflow is reduced. Still further, as indicated by
the arrow A4 in FIG. 4, the labyrinth gap formed by the shaft 21,
the sleeve 22, the sealing member 24, and the cover member 12 can
minimize discharge of the airflow, and the rate of airflow
discharged from the pivot assembly bearing device 2 to the outside
can be further reduced. Still another further, the cut-out portion
24a1 formed at an upper portion of the sealing member 24 forms an
enlarged gap portion at an intermediate portion of the labyrinth
gap. The flow rate of the airflow is reduced in the enlarged gap
portion, and the flow rate of the airflow is further reduced in the
proximity of the outlet, and thus, the flow rate of the airflow
discharged from the pivot assembly bearing device 2 to the outside
can be further reduced. In the present embodiment, the cut-out
portion 24a1 is provided in the corner between the upper surface
24a and the outer peripheral surface of the sealing member 24, but
the cut-out portion 24a1 may be provided between the upper surface
24a and the inner peripheral surface of the sealing member 24.
[0036] Therefore, the out-particles retained in the pivot assembly
bearing device 2 can be kept from being scattered by airflow to the
outside of the pivot assembly bearing device 2, and thus the
cleanliness in the hard disk drive 1 can be kept from being
deteriorated by the scattered out-particles. In FIG. 4, only
airflow in an upper portion of the hard disk drive 1 is
illustrated, but also in a lower portion of the hard disk drive 1,
the labyrinth gap is formed by the sleeve 22, and the convex
portion 11a of the base member 11. Therefore, also in the lower
portion of the hard disk drive 1, the flow rate of the airflow
discharged from the pivot assembly bearing device 2 to the outside
is reduced, and the out-particles can be kept from being scattered
by the airflow to the outside of the pivot assembly bearing device
2. Furthermore, in the present embodiment, the labyrinth gaps are
formed at both of the upper and lower portions of the hard disk
drive 1, but the labyrinth gap may be formed at any of the upper
and lower portions of the hard disk drive 1.
First Modification
[0037] FIG. 5 is a cross-sectional view of a configuration of a
modification of the pivot assembly bearing device illustrated in
FIG. 2. In the above embodiment, the annular sealing member 24 is
disposed at the upper portion of the upper rolling bearing 23, but,
as illustrated in FIG. 5, the sealing member 24 may be omitted so
that an upper end surface of the upper rolling bearing 23 may be
disposed opposite to the lower surface 12a2 (protruding surface) of
the convex portion 12a of the cover member 12. In such a
configuration, since the labyrinth gap is formed between the sleeve
22 and the cover member 12, the out-particles retained in the pivot
assembly bearing device 2 can be kept from being scattered by
airflow to the outside of the pivot assembly bearing device 2.
Furthermore, according to such a configuration, a distance between
the upper rolling bearing 23 and the lower rolling bearing 23 can
be increased by the thickness of the omitted sealing member 24, and
axial rigidity of the pivot assembly bearing device 2 can be
increased. Alternatively, the whole length of the sleeve 22 can be
reduced by the thickness of the omitted sealing member 24, and
thus, the hard disk drive advantageously can have a reduced
thickness.
Second Modification
[0038] FIGS. 6 to 8 are cross-sectional views of configurations of
modifications of the cut-out portion illustrated in FIG. 3. In the
first embodiment, the inclined surface is formed at a corner of the
upper surface 24a of the sealing member 24 to provide the cut-out
portion 24a1. However, as illustrated in FIG. 6 or 7, a curved
surface instead of the inclined surface may be formed at a corner
of the upper surface 24a of the sealing member 24 to provide a
cut-out portion 24a2 or 24a3. Further, as illustrated in FIG. 8, a
step may be formed at a corner of the upper surface 24a of the
sealing member 24 to form a cut-out portion 24a4. The cut-out
portion may be formed also in the inner peripheral surface of the
sealing member 24. As described above, the cut-out portion may be
formed into any shape and at any position, as long as the cut-out
portion is formed in the upper surface 24a or the inner peripheral
surface of the sealing member 24, the enlarged gap portion is
formed in the intermediate portion of the labyrinth gap, and the
enlarged gap portion reduces the flow rate of the airflow.
Second Embodiment
[0039] Next, a configuration of a pivot assembly bearing device
according to a second embodiment of the present invention is
described with reference to FIG. 9. FIG. 9 is a cross-sectional
view of a configuration of the pivot assembly bearing device
according to the second embodiment of the present invention. The
pivot assembly bearing device according to the second embodiment of
the present invention is different from the pivot assembly bearing
device according to the first embodiment only in configurations of
the sleeve 22 and the mounting hole 31 of the swing arm. Thus, only
the configurations of the sleeve 22 and the mounting hole 31 of the
swing arm are described below.
[0040] As illustrated in FIG. 9, in the present embodiment, the
lower end surface 22d of the sleeve 22 is disposed, through a gap,
opposite to an upper surface 11a2 (protruding surface) of convex
portion 11a formed at the base member 11 on the lower side, and the
upper end surface 22f of the sleeve 22 is disposed, through a gap,
opposite to the lower surface 12a2 (protruding surface) of the
convey portion 12a formed on the cover member 12 on the upper side.
Further, an upper end portion 31a and a lower end portion 31b
around the mounting hole 31 are disposed, through gaps, opposite to
the inner surface 12b of the cover member 12 and the inner surface
11b of the base member 11, respectively. Still further, an upper
inner peripheral surface 31c and a lower inner peripheral surface
31d of the mounting hole 31 are disposed, through gaps, opposite to
the outer peripheral surface 12a1 of the convex portion 12a and the
outer peripheral surface 11a1 of the convex portion 11a.
[0041] As described above, in the present embodiment, a labyrinth
gap is formed on the upper side of the pivot assembly bearing
device 2, between the upper end portion 31a around the mounting
hole 31 and the inner surface 12b of the cover member 12, the upper
inner peripheral surface 31c of the mounting hole 31 and the outer
peripheral surface 12a1 of the convex portion 12a, and the upper
end surface 22f of the sleeve 22 and the lower surface 12a2
(protruding surface) of the convex portion 12a. Furthermore, a
labyrinth gap is formed on the lower side of the pivot assembly
bearing device 2, between the lower end portion 31b around the
mounting hole 31 and the inner surface 11b of the base member 11,
the lower inner peripheral surface 31d of the mounting hole 31 and
the outer peripheral surface 11a1 of the convex portion 11a, and
the lower end surface 22d of the sleeve 22 and the upper surface
11a2 of the convex portion 11a.
[0042] Therefore, also in the present embodiment, the out-particles
retained in the pivot assembly bearing device 2 can be kept from
being scattered by airflow to the outside of the pivot assembly
bearing device 2, and thus the cleanliness in the hard disk drive 1
can be kept from being deteriorated by the out-particles.
Furthermore, in the present embodiment, the labyrinth gaps are
formed at both of the upper and lower portions of the hard disk
drive 1, but the labyrinth gap may be formed at any of the upper
and lower portions of the hard disk drive 1.
Third Modification
[0043] FIG. 10 is a cross-sectional view of a configuration of a
modification of the pivot assembly bearing device illustrated in
FIG. 9. In the second embodiment, the sleeve 22 is disposed between
the shaft 21 and the mounting hole 31. However, the sleeve 22 may
be omitted and a spacer member 26 configured to position the
rolling bearings 23 may be provided between the upper and lower
rolling bearings 23, as illustrated in FIG. 10. According to such a
configuration, the outer diameter of the shaft 21 can be increased
by a thickness of the omitted sleeve 22 in order to increase the
axial rigidity of the pivot assembly bearing device, or the pivot
assembly bearing device 2 can have a size reduced by the thickness
of the omitted sleeve 22, without changing the outer diameter of
the shaft 21.
[0044] For the pivot assembly bearing device according to the first
embodiment of FIG. 2 (Implemented Example), maximum flow rates of
outward airflow in the proximity of the outlet of the labyrinth gap
at the upper portion and outward airflow in the proximity of the
outlet of the labyrinth gap at the lower portion were evaluated by
fluid analysis, changing the gap width "a" of the axial gap and the
gap width "b" of the radial gap near each of the upper and lower
outlets of the labyrinth gaps. FIG. 4 shows the gap width "a" of
the axial gap, the gap width "b" of the radial gap, and outward
airflow A4 in the labyrinth gap at the upper portion. The gap width
"a" of the axial gap, the gap width "b" of the radial gap, and
outward airflow in the labyrinth gap at the lower portion is
similar to FIG. 4. In addition, with respect to a conventional
pivot assembly bearing device illustrated in FIG. 12, maximum flow
rates of outward airflow (airflow A2 illustrated in FIG. 13) around
an outlet of a labyrinth gap at an upper portion and outward
airflow around an outlet of a labyrinth gap at a lower portion were
also determined by fluid analysis. Evaluation results of comparison
between a maximum flow rats in a conventional example and maximum
flow rate in the Implemented Example are illustrated in FIG. 11. In
this evaluation, the gap width "a" is equal to the gap width "b" at
both the lower portion and the upper portion. Note that, numerical
values in the Implemented Example in FIG. 11 represent the ratio of
the maximum flow rate of airflow in the Implemented Example
compared to the maximum flow rate of airflow in the conventional
example. That is, the maximum flow rate of the conventional example
corresponds to 100% in FIG. 11. In FIG. 11, the upper outlet
represents the area of the radial gap which is located near the
upper end surface of the sleeve in the labyrinth gap formed at the
upper portion of the pivot assembly hearing device illustrated in
FIG. 2, and the lower outlet represents the area of the radial gap
area which is located near the lower end surface of the sleeve in
the labyrinth gap formed at the lower portion of the pivot assembly
bearing device illustrated in FIG. 2.
[0045] As illustrated in FIG. 11, in the Implemented Example, the
maximum flow rates of the outward airflow are reduced at the upper
outlet and the lower outlet as the widths "a" and "b" are reduced,
compared with the conventional example. Therefore, according to the
pivot assembly bearing device of the Implemented Example, it was
confirmed that formation of the labyrinth gap suppresses discharge
of airflow from the outlet side of the pivot assembly bearing
device, and the out-particles generated in the pivot assembly
bearing device can be kept from scattering outside. In addition, it
is predicted from FIG. 11 that when the gap width is not less than
0.37 mm, the maximum flow rate at the lower outlet in the
Implemented Example is equal to that of the conventional example.
Accordingly, in order to reduce scattering of the out-particles to
the outside, the gap width is preferably less than 0.37 mm in the
proximity of the outlets of the labyrinth gaps at the upper and
lower portions.
[0046] The hard disk drive and the pivot assembly bearing device
according to the embodiment of the present invention can minimize
the deterioration of the cleanliness in the hard disk drive caused
by the out-particles originated from the pivot assembly device.
[0047] Although the invention has been described with respect to
specific embodiments for a complete and clear disclosure, the
appended claims are not to be thus limited but are to be construed
as embodying all modifications and alternative constructions that
may occur to one skilled in the art that fairly fall within the
basic teaching herein set forth.
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